Computing devices, such as notebook computers, personal data assistants (PDAs), and mobile handsets, have user interface devices, which are also known as human interface device (HID). One user interface device that is common is a touch-sensor button. A basis touch-sensor button emulates the function of a mechanical button. Touch-sensor buttons may be embedded into different types of operational panels of electronic devices. For example, touch-sensor buttons may be used on operational or control panels of household appliances, consumer electronics, mechanical devices, and the like. Touch-sensor buttons may also be used in conjunction with, or in place of, other user input devices, such as keyboards, mice, trackballs, or the like.
FIG. 1A illustrates a conventional sensing device having three touch-sensor buttons. Conventional sensing device 100 includes button 101, button 102, and button 103. These buttons are conventional touch-sensor buttons. These three buttons may be used for user input using a conductive object, such as a finger.
FIG. 1B illustrates a conventional sensing device of three touch-sensor buttons 101-103 coupled to a processing device 110. Processing device 110 is used to detect whether a conductive object is present on either, or none, of the touch-sensor buttons 101-103. To detect the presence of the conductive object, the processing device 110 may include capacitance sensors 104-106, which are coupled to buttons 101-103, respectively. The capacitance sensors of the processing device are coupled to the touch-sensor buttons in a one-to-one configuration. Accordingly, the processing device 110 scans the touch-sensor buttons 101-103 using the capacitance sensors 104-106, and measures the capacitance on the touch-sensor buttons 101-103.
Each of the conventional touch-sensor buttons 101-103 may be made of a sensor element of conductive material, such as copper-clad. The conductive material may be form shaped in a circular shape (illustrated in FIG. 1A), or even in a rectangular shape (illustrated in FIG. 1B). The touch-sensor buttons may be capacitance sensor buttons, which may be used as non-contact switches. These switches, when protected by an insulating layer, offer resistance to severe environments.
It should be noted that the conventional configuration of FIG. 1B includes a one-to-one configuration of touch-sensor buttons to capacitance sensors. There are other conventional configurations that may use less capacitance sensors to measure the capacitance on the three touch-sensor buttons. These conventional configurations, however, still require a one-to-one configuration of pins to touch-sensor buttons. Accordingly, by adding more buttons, the processing device needs to have more pins to correspond to the one-to-one configuration of pins to touch-sensor buttons. Similarly, by increasing the pin count, the scan time to scan the sensor elements increases. In addition, the memory of the processing device, which may be used to store program data and/or temporary data (e.g., raw measurement data, differential counts, baseline measurement data, and the like), increases by increasing the pin count.